Diabetic retinopathy is among the most debilitating manifestations of diabetes and is the leading cause of adult blindness in the United States. Remarkably few studies have examined the natural history of retinopathy in the general population of diabetics; rather, most investigations have been clinic based. There have been no such studies among Mexican Americans who have age- and sex-specific diabetes prevalences which are three- to five-fold higher than the U.S. population at large. We propose to investigate the dynamics and risk factors of change in retinopathy status in a cohort of 300 non-clinic based Mexican American diabetics residing in Starr County, Texas. Of the 300, some 220 were identified through random household sampling and from whom we have obtained extensive data through physical examination and fundus photography. In this sample, 28% had diabetic retinopathy. An additional 80 diabetics will be added to this group through random sampling in Starr County during ongoing investigations of gallbladder disease. The total group of diabetics will be given annual examinations which will include: slit-lamp biomicroscopy, dilation and fundus photography of seven standard fields; electrocardiogram; evaluation of body mass and fat distribution; blood pressure, lipids, fasting blood glucose, glycosylated hemoglobin, and linoleic acid level determinations; ultrasound examination of the carotid arteries; and collection of historical information. Each participant will also be visited quarterly to obtain capilary blood specimens for evaluation of fasting blood glucose, glycosylated hemoglobin, hemoglobin, cholesterol, triglycerides, blood pressure, body mass and historical updates. This series of annual examination and in home visitation will provide 9 years of follow-up on the previously identified group and 2 to 4 years on the newly identified group. These data will permit quantitation of the natural history and estimation of the incidence of retinopathy and identification of risk factors for retinopathic change. Specific risk factors to be evaluated include: the degree of short and long term control of blood sugar levels, variability of control, lipid levels, diabetic familiality, blood pressure and the interactions of each with duration of diabetes. Such results will suggest intermediate points at which intervention could be aimed to alter the progression and lessen the impact of retinopathy.